Vehicles commonly include electrically powered window winders. If an obstruction is present, the travel of the window must be interrupted. Standard FMVS 118 requires that the maximum pinching force on obstructions of 20 or 65 N/mm is less than 100 N.
French patent FR-B-2 675 613 discloses a mechanical anti-pinch solution. U.S. Pat. No. 5,955,854 discloses an obstruction detection device for a window or another type of power driven openable member. A transmitter/receiver with infrared diodes is located near the front lower corner of the window. When an obstruction is present in the path of the window, the reflected energy increases. The reflected energy can be used to determine if an obstruction is present in the path of the window. When the window is automatically closed, the transmitter transmits a series of 38 kHz pulses (which are frequency modulated over a lower frequency pulse train) with a period P and a 50% duty cycle. The duration of the low frequency pulses is measured at the receiver output. If no obstruction is present, the duration of a pulse at the receiver output is half the period P. If an obstruction is present, the duration of the pulse at the receiver output increases. The obstruction is detected by comparing the duration of a receiver output pulse with a reference duration. The reference duration can be a function of the position of the window, and it may be generated when either the system is connected to the vehicle battery or at the user's command.
Ambient light can affect the detection of the obstruction, and the effects of ambient light can be overcome by detecting the ambient light with another receiver. The detected ambient light is then subtracted from the signal provided by the infrared receiver.
A drawback to this system is that it employs contactless detection, which is not very reliable. U.S. Pat. No. 5,955,854 discloses detecting the characteristics of the window drive motor as a fallback solution, without providing any details.
U.S. Pat. No. 6,154,149 discloses a camera mounted on the exterior rear view mirrors that detects crime, coupled with pattern recognition algorithms. If the field of the camera covers both sides of the plane of the window, the camera can detect any obstructions on both sides of the window and in the path of the window.
U.S. Pat. No. 5,506,567 discloses an infrared alarm for the surveillance of automobile vehicle windows. A transmitter located on the top of the pillar separating the front and rear windows generates modulated infrared beams. The reflected pulse is received by a detector located next to the transmitter. This document is limited to applications such as alarms.
Obstruction detection applies not only to windows, but also to other types of moving openable members, such as for power driven sunroofs.
A simple, reliable and effective obstruction detection system is therefore desired.